Distillation of alcohol and other two-component mixtures has been well known in the past. For centuries, people have been skilled in the art of alcohol distillation. However, many such prior art devices and systems have not been very energy efficient. For example, most distillation systems or stills require the input of energy to produce steam or vapor needed by the process and then later in the system have used cooling water to extract that energy as waste heat.
Some prior art devices use mechanical compression to elevate the condensation temperature of the vapor so that the heat of vaporization can be recovered. Also, some prior art devices have used heat exchangers to extract heat from the distillate as well as from the bottoms. In spite of these improvements in some prior art devices, however, the devices previously known have not taken full advantage of recoverable energy in the effluent streams. Nothing in the prior art has come very close to a "total heat recovery" design.
An example of a typical prior art distillation system is described in U.S. Pat. No. 1,822,454 to E. Ricard et al. This device appears to be capable of functioning well but does not use vapor compression to recover the heat of vaporization.
A more efficient system is disclosed in U.S. Pat. No. 2,589,406 to A. Latham, Jr. However, Latham's system is suitable only for one-component distillation (i.e., evaporation) since he states that the resistance to internal flow is sufficient to provide the needed backpressure which can be true only for systems where the liquid and vapor have essentially the same boiling/condensation temperature. Also, his system provides no means for enrichment of the vapor in a two-component system. Latham's liquid heat exchanger was not configured to extract maximum energy from the distillate and bottoms, and his on/off control system provided a rollercoaster type of control, making establishment of equilibrium difficult. Latham's device was an efficient one during the World War II era, but it is not sufficient for today's requirements.
Another prior art distillation system is shown in U.S. Pat. No. 3,032,481 to Harding. The Harding device differs from Latham's in that it specifically provides for enrichment of the vapors. However, Harding specifies components such as a steam-heated reboiler and an air-cooled condenser which make his device relatively inefficient.
Therefore, the object of this invention is to develop a system incorporating an improved heat exchanger arrangement which would recover substantially all the heat which is practical to extract from the effluents in the system before they are diverted to storage or disposal. A further object is to incorporate several components and features which would improve the overall efficiency and reliability of the system beyond anything known in the past.